Optics John Arthur, SLAC & William W. Craig, LLNL April 24, 2002 Facility Optics Fixed Masks, Slits/Collimator, Gas & Solid Attenuators, Local Apertures, Low Energy Mirror System, Monochromator End-Station Optics K-B Mirror System, Refractive lenses, Pulse Split and Delay System, Optics Tanks A2-1 and B2-1 LCLS DOE Review, April 24, 2002 John Arthur, SLAC

1.3.1.3 Facility Optics Cost Estimate (FY02 Dollars, Thousands) Name PED Construction Contingency Total 1.3.1.1.3 $ 1,155 - $ 292 $ 1,447 1.3.1.3.1 Fixed Mask $ 62 $ 15 $ 77 1.3.1.3.2 Slits/Collimator A $ 501 $ 87 $ 588 1.3.1.3.3 Slits/Collimator B $ 557 $ 122 $ 679 1.3.1.3.4 Gas Attenuator $ 1,166 $ 186 $ 1,352 1.3.1.3.5 Local Apertures $ 301 $ 71 $ 372 1.3.1.3.6 Wedge Attenuator $ 322 $ 73 $ 395 1.3.1.3.7 Low Energy Mirror System $ 832 $ 1,018 LCLS DOE Review, April 24, 2002 John Arthur, SLAC

1.3.1.4 End Station Optics Costs (FY02 Dollars, Thousands) Name PED Construction Contingency Total 1.3.1.1.4 $ 561 - $ 139 $ 700 1.3.1.4.1 KB Mirror System $ 468 $ 117 $ 586 1.3.1.4.2 Optics Tank A2 $ 392 $ 81 $ 473 1.3.1.4.3 Optics Tank B2 $ 184 $ 28 $ 212 1.3.1.4.4 Refractive Lenses $ 291 $ 70 $ 362 LCLS DOE Review, April 24, 2002 John Arthur, SLAC

1.3.1.5 Crystals and Gratings (FY02 Dollars, Thousands) Name PED Construction Contingency Total 1.3.1.1.5 $ 382 - $ 112 $ 493 1.3.1.5.1 Crystal Monochromator $ 89 $ 28 $ 117 1.3.1.5.2 Pluse Split and Delay $ 159 $ 36 $ 195 LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Optical Elements by Function Confinement  (masks, slits, local apertures) Intensity attenuation  (gas attenuator, solid attenuator) Focusing  (K-B mirror, zone plate) Spectral filter  (mirror low-pass filter, monochromator) Temporal filter  (pulse split/delay) LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Fixed Masks Limit angular divergence of all transmitted radiation Contain all radiation within vacuum beam pipe No coherent radiation will strike these masks Wings of spontaneous radiation will be intercepted Power density low, standard X-ray absorber okay Parameters: Aperture = 4.5 mm diameter round Located 9m and 28m from undulator: transmit 240 µrad (FWHM) LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Adjustable High-Power Slits Intended to intercept spontaneous beam, not FEL beam -- but will come very close, so peak power is an issue Two concepts being pursued for slit jaws Treat jaw as mirror (high-Z material) Treat jaw as absorber (low-Z material Either concept requires long jaws with precision motion Mechanical design based on SLAC collimator for high-energy electron beam LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Local Apertures Used to eliminate stray radiation locally in experimental hutches Laminate structure mitigates peak power issue Will withstand direct FEL beam in experimental hutches LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Optical Elements by Function Confinement  (masks, slits, local apertures) Intensity attenuation  (gas attenuator, solid attenuator) Focusing  (K-B mirror, zone plate) Spectral filter  (mirror low-pass filter, monochromator) Temporal filter  (pulse split/delay) LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Gas Attenuator For use when solid absorber risks damage (low-E FEL, front end) Windowless, adjustable attenuation Can provide up to 4 orders of magnitude attenuation LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Solid Attenuator B4C attenuators can tolerate FEL beam at E > 4 keV in FEE, and at all energies in experimental hutches Linear/log configurations Can be wedged in 2 dimensions for continuously variable attenuation Translation stages provide precision X and Y motion LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Optical Elements by Function Confinement  (masks, slits, local apertures) Intensity attenuation  (gas attenuator, solid attenuator) Focusing  (K-B mirror, zone plate) Spectral filter  (mirror low-pass filter, monochromator) Temporal filter  (pulse split/delay) LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Kirkpatrick-Baez Mirror Focusing K-B mirror systems have proven ability to focus LCLS-size beams to sub-micron dimensions Even smaller focus will come from improved control of mirror figure Control through mirror shape and bending moments X-ray metrology helps understand figure LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Refractive Lens Focusing 10 µm spot needed for plasma experiments; smaller focus possible LLNL prototype, cut into aluminum with diamond tool Calculated phase profile of graphite lens LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Optical Elements by Function Confinement  (masks, slits, local apertures) Intensity attenuation  (gas attenuator, solid attenuator) Focusing  (K-B mirror, zone plate) Spectral filter  (mirror low-pass filter, monochromator) Temporal filter  (pulse split/delay) LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Mirror Low-Pass Filter Use to reduce higher harmonics of FEL radiation Place mirror cutoff energy above FEL fundamental, below 3rd harmonic Two-mirror system will reduce harmonic content by 4-5 orders of magnitude Can achieve needed figure with Si, will try Be coating on Si to better tolerate peak power LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Diffraction Monochromator Needed when LCLS bandwidth (10-3) is too large for energy resolution or coherence length requirements Crystal monochromator has bandwidth 10-5-10-4 Multilayer monochromator has bandwidth 10-3-10-2 Peak power considerations: No problem in Hall B; Si questionable in Hall A, but Be, B, C will definitely work Average power at monochromator < 1 W; not a problem LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Optical Elements by Function Confinement  (masks, slits, local apertures) Intensity attenuation  (gas attenuator, solid attenuator) Focusing  (K-B mirror, zone plate) Spectral filter  (mirror low-pass filter, monochromator) Temporal filter  (pulse split/delay) LCLS DOE Review, April 24, 2002 John Arthur, SLAC

Pulse Split/Delay System Thin Si(400) acts as beam splitter at 8 keV 10 µm Si crystal reflects >80% within BW~2x10-5 Outside this bandwidth, transmits 75% Tune upper and lower paths to slightly different energies within LCLS BW of 10-3 Single translation stage changes relative path lengths 54 mm translation along indicated direction ~ 500 ps change in delay 1 µm resolution ~ 10 fs resolution LCLS DOE Review, April 24, 2002 John Arthur, SLAC